1. Field of the Invention
The present invention relates to a restricting blade, a light quantity adjusting device, an optical apparatus, and a method for manufacturing a restricting blade, and in particular, relates to a restricting blade used in a light quantity adjusting device which adjusts light quantity by varying an aperture diameter centered on an optical axis, a light quantity adjusting device using the restricting blade, an optical apparatus including the light quantity adjusting device, and a method for manufacturing the restricting blade.
2. Description of the Related Art
A light quantity adjusting device (iris) is incorporated in an optical apparatus such as an imaging apparatus like a video camera, a still camera or the like, and a projecting apparatus like a projector and is used for adjusting light quantity such as photographing light quantity and projecting light quantity. Here, a plurality of light quantity adjusting blades (hereinafter, called restricting blades) are placed openably and closably at a substrate which has an optical axis aperture on a photographing optical path (or a projecting optical path). Light quantity is adjusted by adjusting an aperture centered on an optical axis to have a large diameter or a small diameter.
As illustrated in FIG. 13A, in general, a restricting blade 21 is configured to include a blade substrate 21w and a blade end face 21u which defines an aperture diameter as being an end face of the blade substrate 21w. Similarly to other members in an optical apparatus, when undesirable internal reflection occurs at the blade end face 21u, image quality is decreased with occurrence of flare, ghost, or the like.
As illustrated in FIG. 13B, in a case that the blade end face 21u has a face parallel to an optical axis O, incoming light from the outside is reflected at the blade end face 21u, so that the reflected light undesirably reaches a sensor side. As illustrated in FIG. 13C, it is ideal that the restricting blade 21 has the blade end face 21u which does not has a face parallel to the optical axis O. For example, it is ideal that the blade end face 21u is processed to be completely oblique.
Conventionally, contrivance has been performed variously to prevent undesirable incidence of reflection light to a sensor side by processing a shape of a blade end face.
It is difficult to process a thin restricting blade (e.g., thickness of 60 μm) into a completely oblique shape. For example, Japanese Patent Application Laid-Open No. 56-012629 discloses a technology to perform cutting after performing face-pressing and Japanese Patent Application Laid-Open No. 2011-059237 discloses a technology to cut a blade end face with blast processing. Further, Japanese Patent Application Laid-Open No. 2002-229095 discloses a restricting blade in which a blade end face has a plurality of stepped portions with mold-forming.
However, with the technology of Japanese Patent Application Laid-Open No. 56-012629, since a surplus part is cut after a blade end face is formed into a tapered shape with face-pressing, there is a fear that reflected light undesirably reaches a sensor side owing to formed cut face. Another embodiment thereof discloses a method to cut a blade end face with punching while setting a blade member which is to be material of a restricting blade in a slanted state. However, there is a fear that accuracy is decreased owing to that the blade member is set in a slanted state. With the technology of Japanese Patent Application Laid-Open No. 2011-059237, there is a problem that cost is prone to increase owning to difficulty for mass production due to long required time for each blasting. Further, although a restricting blade having an end face formed stepwise is manufactured with forming processing with the technology of Japanese Patent Application Laid-Open No. 2002-229055, a thin restricting blade as described above cannot be manufactured with mold-forming.